This invention relates to methods and apparatus for directing a movable cutting tool, and more particularly relates to an assembly for manipulating a powered router bit according to a preselected design.
It is conventional to employ a jig and the like to direct the movement of a powered cutting tool, and it is further conventional to employ a powered router bit to cut a design into the surface of a work piece according to a preselected design such as a template or pattern. More particularly, it is within the scope of the prior art to manipulate the router bit by guiding the tip of a stylus according to a design or pattern within a plane associated with the work piece.
In operating this type of equipment, the stylus and cutting bit are linked together so that when the stylus is moved either laterally or vertically, according to the pattern sought to be followed, the cutting bit will move against the work piece in precise conformity with the action of the stylus. However, this requires that the cutting bit not only move axially the same as the stylus, it further requires that the bit is continually positioned exactly as the stylus with respect to all three axes of both the pattern and the work piece. In particular, the bit must not only move the same as the stylus according to the X and Y axes of the pattern and work piece, the bit must also be maintained in alignment with the Z-axis the same as the stylus.
Those having experience with equipment of this type will readily appreciate that there is an ever present problem in maintaining the relationship of the bit to the stylus, while the router bit is engaging the work piece. This is because the router bit is arranged to rotate about the Z-axis, while the design sought to be followed requires the bit to move according to the X and Y axes of the pattern. It is apparent that merely driving the bit against the work piece will, by itself, tend to tilt the bit. However, rotation of the router bit alone imparts heavy torque to the bit, and when the rotating bit moves against the work piece according to X and Y axes, this torque also tends to tilt or otherwise further misalign the bit with respect to the Z-axis of the pattern which is sought to be followed. This is especially the case whenever the bit is moved along the Z-axis as well as in conjunction with being moved with respect to the X and Y axes of the work piece.
The problem is especially troublesome whenever time is significant factor in producing a finished item, since the extent of such misalignment is a function of both the force with which the router bit is driven against the work piece, and the hardness or toughness of the material being cut by the router bit. Thus, the extent of such misalignment depends on a combination of these factors, and when such factors increase to a sufficient extent, it has been found that the assembly holding the bit and directing its movement tends to warp or deform relative to the plane of the material sought to be cut, whereby the finished product does not conform to the pattern.
There are, of course, routers which will produce precision shaped products on a mass production basis, notwithstanding the problems hereinbefore described. In these devices, however, misalignment of the bit has been prevented simply by mounting it in a massive, and therefore expensive chassis which, in turn, often requires powered apparatus to operate. In addition, many routers in the prior art are also unsuitable from a safety standpoint, for the reason that the hands of the operator are not sufficiently shielded from the bit action, and hence these routers constitute a potential hazard to the operator and anyone close to the device.
Devices of this types are, of course, inherently not suitable or within the capability of many potential operators having a need for equipment which is not only cheaper but easier to use. Until now, however, no such device has been available notwithstanding this continued need.
These disadvantages of the prior art are overcome with the present invention, and commercially acceptable embodiments of a machine with a revolving vertical spindle and cutter for milling out the surface of wood, metal, and the like are herein provided which are not only fully capable of milling out the surfaces of work pieces under most operating conditions, but which are also capable of other tasks completely beyond the capabilities of the machines of the prior art. More particularly, however, the embodiments of the present invention are capable of operation with a much higher efficiency and at a substantially reduced cost of construction and operation.